This week’s green light signal from New Horizons tells us that it’s continuing its mission through the Kuiper Belt. At the present time, the spacecraft is 40.55 astronomical units from the Sun and just under 3 AU from its next target, 2014 MU69. It’s moving at 14.19 kilometers per second and at that rate will get to MU69 on December 31, 2018. To give you some perspective on where it is in the Kuiper Belt, the inner edge of this distant region is about 30 AU and the outer edge is around 50 AU. So, the spacecraft is well within the third “regime” of the solar system. (Note: an astronomical unit is the distance between Earth and the Sun, 150 million kilometers.)
Deducing the Kuiper Belt
The chart of the Kuiper Belt, showing its shape and extent beyond Neptune. Courtesy NASA.
Planetary scientists haven’t always known the Kuiper Belt existed. However, the discovery of Pluto suggested that there might be more bodies beyond Neptune, populating a region between that planet and the Oort Cloud (the most distant reaches of the solar system). That got people to thinking about a theoretical population of objects dubbed “Trans-Neptunian Objects”, or TNOs. Today, some ...